Requirements of modern electronics, such as cellular telephones or medical devices, demand more functions packed into a product while paradoxically providing less physical space in the system for the increased content. Continuous cost reduction is another requirement. Some technologies primarily focus on integrating more functions into each integrated circuit or stacking these integrated circuits into a single package. Other technologies provide different functions, such as optical or microelectromechanical, than conventional integrated circuits. While these technology approaches provide different form functional solutions, they do not address the requirements for cost reduction.
One proven way to reduce cost is to use mature package technologies with existing manufacturing methods and equipments, or in some cases eliminate some of the existing steps and equipments. Paradoxically, the reuse of existing manufacturing processes does not provide a robust and reliable packaging solution for microelectromechanical systems (MEMS) or for optics. Still the demand continues for lower cost, smaller size, and more functionality.
MEMS take the advantage of the silicon's mechanical properties or both mechanical and electrical properties. MEMS are actual mechanical systems that are created via a process called micro machining. Micro machining allows a two-dimensional or three-dimensional mechanical system to be created in a similar area that a typical integrated circuit would use. MEMS comprise mechanical structures, such as microactuators, microsensors, and microelectronics, integrated into a chip.
The diverse nature of MEMS technology complicates packaging to the extent that the packaging and testing cost may reach as high as 90% of the MEMS total fabrication cost. MEMS device packages may contain many electrical and/or mechanical components. The differences of MEMS from conventional semiconductors include the surface of the MEMS device must be free to allow mechanical movement and is very sensitive to mechanical damage as well as to damage from particle contamination.
Protection is a key element in packaging MEMS because ingress of moisture or contamination can prevent the devices from working. A used protection method in MEMS packaging is to use ceramic, metal or plastic lid or silicon cover or glass, which must be accompanied by special features like an epoxy dam to lift the cap or cover up from the die surface. The epoxy dam and other approaches are processing steps that differ from the high volume, low cost integrated circuit and packaging manufacturing processes. These differences are challenges to reduce cost of manufacturing and packaging MEMS devices.
Thus, a need still remains for a robust and reliable packaging solution for MEMS devices providing low cost manufacturing as well as reduce the package height. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.